The present invention relates to surface fabricating of a semiconductor and a metal.
An example of surface fabricating is etching of semiconductors. It is known to etch semiconductors with plasma and to control the surface reaction of the plasma with the semiconductor by introducing and mixing oxygen or nitrogen into the plasma of a reactive gas. Such a technique is discussed, for example, in J. Vac. Sci. Technol. B1 23 (1983). The method described therein mixes O.sub.2 or N.sub.2 into the plasma of SF.sub.6 or the like and conducts etching. SiO or Si--N is formed during the reaction and prevents etching of the sidewall of the etching hole. This plasma etching involves high energy ions, of some dozens of eV to several hundreds or even a thousand eV, which are implanted into the surface of the substrate during etching by use of plasma. Charge damage or mechanical damage to the substrate surface raises problems as is known. In plasma etching, a material is turned into a plasma consisting of ions and charged particles. Adjacent the substrate, a high voltage will accelerate the plasma into the substrate. Mechanical damage can occur, for example, the silicon to silicon bonding can be broken, causing damage in the crystalline structure of a silicon substrate. Also, charge damage can occur, for example, the charged particles can cause charge particles in the interface between silicon oxide and silicon in a MOS device, to seriously affect its performance in a disadvantageous way.
Japanese Patent Laid-Open No. 113775/1986 does not use plasma and therefore does not damage the N-type substrate surface, but instead uses a heated beam of reactive gas for etching the substrate. The heated gas beam may be a neutral particle beam so that there is no charge damage and since the energy of this beam is below 1 eV, it hardly mechanically damages the substrate. This method can anisotropically etch undoped silicon (Si) by the use of Cl.sub.2 as a reactive gas. A heated beam of reactive gas, as used in this disclosure, refers to a gas that is chemically reactive to the substrate or in some other way causes an etching in the substrate, which is thermally excited to increase its reaction rate so that it can etch, and which is not a plasma, meaning that it does not contain ions and electrons and is therefor neutral. The term neutral is not referring to chemical neutrality, but rather to charge neutrality.
Japanese Laid-Open No. 62-86732 laid open Apr. 21, 1987 from Application No. 60-226718 filed Oct. 14, 1985, discloses a deposition process, specifically a process for depositing silicon oxide as an insulator on a substrate, with or without a mask. The silicon is projected onto the substrate along with the projection of heated oxygen, which reacts on the surface of the substrate and deposits silicon oxide. The heating of the oxygen is sufficient so that it becomes thermally reactive. In the disclosure, it is felt that some unreacted silicon is also deposited, which will detract from the insulator properties of the film being deposited. Therefore, FIG. 2 of the disclosure uses SF.sub.6 in a heated state, so that unreacted silicon will be removed from the deposited film as it is formed, which in a sense is etching. However, the overall process is one of deposition and not one of etching. The added material SF.sub.6 enhances etching, or more accurately, causes a form of etching.
In Japanese Laid-Open 62-86730 laid open Apr. 21, 1987 from Application No. 60-226722 filed Oct. 14, 1985, it is desired to etch a silicon substrate. SF.sub.6 is projected onto the substrate, but it will not react to effectively produce etching by itself. Addition energy must be provided. Therefor, CO.sub.2, in a thermally excited or heated state, is introduced only for the purpose of providing thermal energy causing the SF.sub.6 to etch the substrate, otherwise the CO.sub.2 is not active and it is not reactive. The added material CO.sub.2 causes the etching to happen, that is increases the etching rate.
The etching rate of Cl.sub.2, in a thermally excited, that is, heated state, can be increased by the addition of ions, electrons or photons, which is electrically assisted etching. The additional material increased the etch rate of the silicon substrate.
Of further interest is Application No. 62-237501 filed Oct. 25, 1985, Laid-Open No. 62-98731, laid open May 8, 1987.